Wafer processing method and chip manufacturing method

Abstract

To reduce burrs when forming processed grooves along the planned dividing lines of a wafer.SOLUTION: A wafer processing method forms a processed groove in a wafer (10) along a planned dividing line (11), in which a structure (13) is formed on at least a part of the planned dividing line, and includes a first processing step of forming a first processed groove (14) that leaves an end portion (30) including at least one end of the planned dividing line of the structure in the width direction, and a second processing step of forming a second processed groove (15) that removes the end portion remaining in the first processing step along the planned dividing line.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a wafer processing method and a chip manufacturing method. [Background technology]

[0002] In a wafer in which chips are formed in multiple areas partitioned by planned dividing lines (streets), if structures such as metal patterns are provided on the planned dividing lines, when processing grooves along the planned dividing lines, burrs are generated as a result of processing the structures on the planned dividing lines and adhere to the chips.

[0003] In the invention disclosed in Patent Document 1, a laser beam is irradiated only onto areas of the planned dividing line where no structures are formed to form a processing groove, and then a modified layer is formed inside the wafer along the planned dividing line.An external force is then applied to the wafer with the processing groove and modified layer formed thereon to divide it along the planned dividing line, thereby suppressing the generation of burrs caused by processing the structures on the planned dividing line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-098296 Summary of the Invention [Problem to be solved by the invention]

[0005] The processing method of forming grooves by avoiding areas where no structures are formed is difficult to apply when the structures occupy a large area relative to the planned dividing line. Therefore, in wafer processing, there is a need to reduce burrs on chips while forming grooves in areas where structures are present.

[0006] An object of the present invention is to provide a wafer processing method and a chip manufacturing method that can reduce burrs when forming grooves along planned dividing lines on which structures are arranged. [Means for solving the problem]

[0007] One aspect of the present invention is a wafer processing method for forming a processing groove in a wafer along a planned dividing line, wherein a structure is formed on at least a portion of the planned dividing line, and the method comprises: a first processing step for forming a first processing groove that leaves an end portion of the structure that includes at least one end of the planned dividing line in the width direction; and a second processing step for forming a second processing groove along the planned dividing line that removes the end portion that remained in the first processing step.

[0008] The first groove and the second groove are preferably formed by irradiating the wafer with a laser beam.

[0009] Preferably, the volume of the structure removed in the first processing step is greater than the volume of the structure removed in the second processing step.

[0010] The output of the laser beam irradiated in the second processing step is preferably smaller than the output of the laser beam irradiated in the first processing step.

[0011] The distance between the centers of adjacent focused spots of the laser beam at the positions where the wafer is irradiated is preferably smaller in the first processing step than in the second processing step.

[0012] The structure left in the first processing step preferably has a length of 2% to 40% of the width of the planned dividing line of the structure.

[0013] One aspect of the present invention is a method for manufacturing chips, in which a wafer is divided by at least one of the first groove and the second groove to manufacture a plurality of chips. [Effects of the Invention]

[0014] According to the above aspect, by leaving the end of the structure in the first processing step and removing the end in the second processing step, it is possible to reduce burrs that adhere to the chip when forming a processing groove along the planned division line. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. [Figure 2] FIG. 2 is an enlarged top view of a portion of the planned dividing lines of the wafer. [Figure 3] FIG. 1 is a diagram showing a laser processing device. [Figure 4] FIG. 10 is a cross-sectional view showing a comparative example of a wafer processing method. [Figure 5] FIG. 10 is a top view showing a comparative example of a wafer processing method. [Figure 6] 1A and 1B are cross-sectional views showing a first embodiment of a wafer processing method. [Figure 7] FIG. 1 is a top view showing a first embodiment of a wafer processing method. [Figure 8] FIG. 10 is a cross-sectional view showing a second embodiment of the wafer processing method. [Figure 9] FIG. 10 is a cross-sectional view showing a third embodiment of the wafer processing method. [Figure 10] 10 is an enlarged top view of a portion of a planned dividing line on a wafer having a different arrangement of structures. FIG. [Figure 11] FIG. 10 is a cross-sectional view showing a fourth embodiment of the wafer processing method. [Figure 12] 1 is a table showing processing conditions and processing results in an embodiment. [Figure 13] FIG. 10 is a cross-sectional view showing a fifth embodiment of the wafer processing method. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, with reference to the accompanying drawings, an embodiment of a wafer processing method and a chip manufacturing method to which the present invention is applied will be described. The Z-axis direction shown in each drawing is the thickness direction of a plate-shaped wafer 10. The X-axis direction and the Y-axis direction are each perpendicular to the Z-axis direction, and the X-axis direction and the Y-axis direction are perpendicular to each other. When processing the wafer 10, the Z-axis direction is the vertical direction, and the X-axis direction and the Y-axis direction are horizontal directions.

[0017] As shown in FIG. 1, the surface of a wafer 10 has a plurality of device regions partitioned in a grid pattern by dividing lines 11 extending in the X-axis direction and the Y-axis direction, and chips 12 are formed in each device region. The dividing lines 11 may also be called streets. The wafer 10 is, for example, a disk-shaped semiconductor wafer or an optical device wafer, and is made of a material such as silicon, sapphire, or gallium arsenide. The chips 12 are semiconductor devices, optical devices, or the like. Note that the material of the wafer 10 and the type of the chips 12 are not limited. The wafer 10 may be a single wafer or a stacked wafer in which multiple wafers are bonded together.

[0018] 2, a TEG (Test Element Group) 13, which is a metal structure, is arranged on at least a part of the grid-like dividing lines 11. The TEG 13 is a test element for evaluating device characteristics before dividing the wafer 10 into a plurality of chips 12, and is formed of a predetermined metal pattern.

[0019] The structure to be placed on the planned dividing line 11 is not limited to a TEG. For example, it can be applied to a case where a metal structure protrudes from the side of a chip, such as a lead of a QFP (Quad Flat Package), and the structure protruding from the chip is placed on the planned dividing line 11.

[0020] 3, a processed groove is formed in the wafer 10 along the planned dividing line 11. The processing device 20 is a laser processing device that performs laser processing, and includes a holding table 21 that holds the wafer 10, a laser irradiation unit 22 that irradiates a laser beam L toward the wafer 10 on the holding table 21, and an imaging unit 23 that images the wafer 10 on the holding table 21.

[0021] Each part of the processing device 20 is controlled by a control unit 24. The control unit 24 has a processor that generates signals for controlling each part of the processing device 20, and a memory that stores various information. The processor controls the operation of each part of the processing device 20 by reading and executing a program stored in the memory. The formation of the processed grooves along the planned division lines 11 is also performed under the control of the control unit 24.

[0022] The holding table 21 has an upward holding surface on which the wafer 10 is placed. The holding surface of the holding table 21 is formed of a porous member that communicates with a suction source (not shown), and the wafer 10 can be sucked and held on the holding surface by operating the suction source.

[0023] The laser irradiation unit 22 focuses the laser beam L emitted by the laser oscillator 25 using the focusing optical system 26, and irradiates the laser beam L downward in the Z-axis direction. Although not shown in FIG. 3, the laser irradiation unit 22 may include a mirror or the like as an element that forms an optical path that guides the laser beam L from the laser oscillator 25 to the focusing optical system 26. The irradiation range of the laser beam L on the focal plane focused by the focusing optical system 26 is defined as the focused spot, and the diameter of the focused spot of the laser beam L is defined as the spot diameter. Furthermore, the distance from the focusing optical system 26 to the focal plane of the laser beam L is defined as the focal length, and the range in the optical axis direction in which the laser beam L focused by the focusing optical system 26 is considered to be focused (the range in the optical axis direction in which the energy of the laser beam L can be obtained most effectively) is defined as the focal depth.

[0024] The laser oscillator 25 oscillates, as the laser beam L, a pulsed laser beam having a wavelength that is absorbed by the wafer 10. When the laser beam L is irradiated along the dividing lines 11, an ablation process is performed at the location of the focused spot of the laser beam L to remove the TEG 13 and the wafer 10, and a processed groove is formed along the dividing lines 11. The processed groove that is formed may be a half-cut groove with a bottom that is deep enough to reach partway through the thickness of the wafer 10, or a full-cut groove that penetrates the wafer 10 in the thickness direction. The control unit 24 controls to change the output of the laser oscillator 25, thereby changing the intensity of the laser beam L.

[0025] The focusing optical system 26 is a variable-focus optical system capable of changing the focal length by moving at least some of the lenses in the optical axis direction using an optical system adjustment unit 27 equipped with a motor or the like. Changing the focal length of the focusing optical system 26 changes the focal depth and spot diameter of the laser beam L. Specifically, as the focal length of the focusing optical system 26 increases, the focal depth and spot diameter increase, and as the focal length of the focusing optical system 26 decreases, the focal depth and spot diameter decrease. The control unit 24 sets the spot diameter of the laser beam L by controlling the operation of the optical system adjustment unit 27.

[0026] As another embodiment of the laser irradiation unit 22, a plurality of optical paths with different focal lengths may be provided, and the spot diameter may be changed by switching the optical path through which the laser beam L passes.

[0027] In the processing examples of FIGS. 5 and 7, the focused spot of the laser beam L is circular, but the focused spot is not limited to a circular shape and may be elliptical or the like.

[0028] The position of the laser irradiation unit 22 can be changed horizontally (in the X-axis direction and the Y-axis direction) relative to the holding table 21 by a horizontal movement mechanism 28. The position of the laser irradiation unit 22 can also be changed vertically (in the Z-axis direction) relative to the holding table 21 by a lifting mechanism 29. The horizontal movement mechanism 28 and the lifting mechanism 29 are configured, for example, by a ball screw mechanism that moves the laser irradiation unit 22 by rotating a ball screw with a motor, or an air cylinder mechanism that moves the laser irradiation unit 22 by the pressure of air supplied from an air source. The control unit 24 controls the horizontal movement mechanism 28 and the lifting mechanism 29 to change the relative positions of the wafer 10 held on the holding table 21 and the laser irradiation unit 22, thereby changing the irradiation position of the laser beam L on the wafer 10.

[0029] The holding table 21 may be configured to be movable in the horizontal direction, and when changing the relative positions of the wafer 10 and the laser irradiation unit 22, not only the laser irradiation unit 22 but also the holding table 21 may be moved by the horizontal movement mechanism 28. For example, the horizontal movement mechanism 28 may be responsible for movement in the X-axis direction, and the movement mechanism of the holding table 21 may be responsible for movement in the Y-axis direction.

[0030] The control unit 24 uses the imaging section 23 to capture an image of the wafer 10 on the holding table 21, and sets the position of the laser irradiation section 22 relative to the wafer 10 based on the captured image.

[0031] In the processing methods of the respective embodiments described below, when setting the spot diameter of the focused spot of the laser beam L, the control unit 24 may set the spot diameter based on the sizes of the TEGs 13, 16 acquired from the captured images of the TEGs 13, 16 captured by the imaging unit 23. Alternatively, data relating to the sizes of the TEGs 13, 16 and the like may be input to the control unit 24 in advance as processing conditions, and the control unit 24 may set the spot diameter by referring to the information in the data.

[0032] Next, a processing method for forming a processed groove along the dividing line 11 on which the TEG 13 is arranged on the wafer 10 will be described. The example shown below is a case where processing is performed on the dividing line 11 extending in the X-axis direction, with the longitudinal direction (extension direction) of the dividing line 11 being the X-axis direction and the width direction of the dividing line 11 being the Y-axis direction. Naturally, the same processing method can be applied not only to the dividing line 11 extending in the X-axis direction but also to the dividing line 11 extending in the Y-axis direction.

[0033] 4 and 5 show a comparative example of a processing method different from the processing methods of the embodiments to which the present invention is applied. In this comparative example of a processing method, as shown in FIG. 4A, the spot diameter Ra of the focused spot Sa of the laser beam L is set to be larger than the length Ha of the TEG 13 in the width direction (Y-axis direction) of the dividing line 11, and the irradiation position of the laser beam L in the width direction of the dividing line 11 is set so that the range of the focused spot Sa covers the entire length Ha of the TEG 13. In other words, the laser processing is set so that the entire TEG 13 is removed in one laser processing to form the processed groove 40. Note that, although FIG. 4A shows the focused spot Sa at a position spaced above the wafer 10, in reality, the irradiation position of the laser beam L in the Z-axis direction is adjusted so that the focused spot Sa reaches the range of the thickness of the wafer 10 (the position of the TEG 13).

[0034] After setting the processing conditions as described above, as shown in Fig. 5, the irradiation position of the laser beam L on the wafer 10 is changed in the longitudinal direction (X-axis direction) of the dividing line 11 so that the distance between the centers of adjacent focused spots Sa is a predetermined distance Ta, whereby the multiple TEGs 13 on the dividing line 11 are sequentially removed by ablation processing using the laser beam L. As a result, as shown in Fig. 4(B), a processed groove 40 in which the TEGs 13 have been removed is formed between adjacent chips 12 across the dividing line 11.

[0035] As shown in FIG. 4B, when the TEG 13, which is a metal structure, is removed by ablation processing using irradiation with a laser beam L, burrs Qa, which are thorn-like protrusions, are generated on both sides of the groove 40. Before removal, the TEG 13 has a length Ha in the width direction of the dividing line 11 that is close to the distance between two adjacent chips 12 on either side of the dividing line 11, and the space between the TEG 13 and the chips 12 on both sides is narrow. Therefore, if a laser beam L having a spot diameter Ra of a focused spot Sa larger than the length Ha of the TEG 13 is used to remove the entire length Ha of the TEG 13 at once, large burrs Qa are generated on the chips 12 located on both sides of the groove 40 as processing marks resulting from removing the TEG 13. Burrs Qa with a large upward height require a long time to be removed by performing a deburring operation after the groove 40 is formed, which lengthens the processing time for the wafer 10.

[0036] Furthermore, in order to remove the large-volume TEG 13 in one laser process, it is necessary to set a high output of the laser beam L. If a high-output laser beam L is irradiated onto the division line 11 with a focused spot Sa having a large spot diameter Ra, the chips 12 on both sides of the division line 11 may be affected by the laser beam L and generate heat, which may result in a decrease in the bending strength of the chips 12.

[0037] Next, wafer processing methods according to the embodiments of the present invention, which differ from the processing methods of the comparative examples described above, will be described. FIGS. 6 and 7 show a processing method according to a first embodiment, FIG. 8 shows a processing method according to a second embodiment, and FIG. 9 shows a processing method according to a third embodiment. FIG. 10 shows a portion of a modified wafer 10 having a different arrangement of structures on the planned dividing lines 11, and FIG. 11 shows a processing method according to a fourth embodiment corresponding to the modified wafer 10. Note that in the cross-sectional views of the respective embodiments ( FIGS. 6 , 8 , 9 , and 11 ), the focused spots Sb, Sc, Sd, Se, and Sf of the laser beam L are shown spaced apart above the wafer 10. However, in practice, the irradiation position of the laser beam L in the Z-axis direction is adjusted so that these focused spots reach the thickness range of the wafer 10 (the positions of TEGs 13 and 16).

[0038] [First processing step] 6A and 7A show a first processing step in the processing method of the first embodiment. As shown in Fig. 6A, in the first processing step, the control unit 24 sets the spot diameter Rb of the focused spot Sb of the laser beam L to be smaller than the length Ha of the TEG 13 in the width direction (Y-axis direction) of the planned division line 11.

[0039] The length Ha of the TEG 13 may be obtained from an image captured by the imaging unit 23, or may be obtained from data included in the processing conditions input to the control unit 24. Numerical values ​​of the spot diameter Rb relative to the length Ha of the TEG 13 are stored in advance in the memory of the control unit 24 as table data. Alternatively, a formula for calculating an appropriate spot diameter Rb from the length Ha of the TEG 13 may be stored in the memory of the control unit 24, and the control unit 24 may calculate the spot diameter Rb by calculation. In either case, the control unit 24 adjusts the focal length of the focusing optical system 26 of the laser irradiation unit 22 so as to correspond to the set spot diameter Rb.

[0040] Next, the control unit 24 sets the position of the laser irradiation unit 22 in the width direction of the planned dividing line 11 so that both end portions of the TEG 13 are not included in the range of the focused spot Sb, and causes the laser beam L to be irradiated toward the wafer 10. As shown in (A) of Fig. 7, the control unit 24 sequentially changes the irradiation position of the laser beam L on the wafer 10 (the position of the focused spot Sb) in the longitudinal direction of the planned dividing line 11 so that the centers of adjacent focused spots Sb are spaced a predetermined distance Tb, and causes the ablation processing by the laser beam L along the longitudinal direction of the planned dividing line 11.

[0041] 6B and 7B, by performing the first processing step, the central portions of each of the multiple TEGs 13 on the division line 11 in the width direction that are included in the range of the focused spot Sb and irradiated with the laser beam L are removed, leaving end portions 30 on both sides in the width direction that are outside the range of the focused spot Sb, and a first processing groove 14 is formed between the end portions 30 on both sides. Burrs Qb generated when forming the first processing groove 14 are attached to the upper portions of the end portions 30. In other words, in the first processing step, the end portions 30 that are left on both sides in the width direction of the division line 11 function as protective walls that prevent burrs from adhering to the chip 12.

[0042] [Second processing step] 6B and 7B show a second processing step in the processing method of the first embodiment. As shown in FIG. 6B, in the second processing step, the control unit 24 sets the focal length of the focusing optical system 26 of the laser irradiation unit 22 so that the spot diameter Rc of the focusing spot Sc of the laser beam L is equal to or greater than the length Ha of the original TEG 13 in the width direction of the division line 11. In other words, the spot diameter Rc of the focusing spot Sc is set so that the laser beam L can be simultaneously applied to the remaining end portions 30 on both sides of the width direction of the division line 11. The numerical value of the spot diameter Rc relative to the length Ha of the original TEG 13 may be stored in the memory of the control unit 24 as table data, or the control unit 24 may calculate the spot diameter Rc from the length Ha of the TEG 13 using a formula. In either case, the control unit 24 adjusts the focal length of the focusing optical system 26 of the laser irradiation unit 22 so as to correspond to the set spot diameter Rc.

[0043] Next, the control unit 24 sets the position of the laser irradiation unit 22 in the width direction of the dividing line 11 so that the range of the focusing spot Sc includes both end portions 30, and causes the laser beam L to be irradiated toward the wafer 10. As shown in (B) of Fig. 7, the control unit 24 sequentially changes the irradiation position of the laser beam L on the wafer 10 (the position of the focusing spot Sc) in the longitudinal direction of the dividing line 11 so that the distance between the centers of adjacent focusing spots Sc is a predetermined distance Tc, thereby causing the ablation processing by the laser beam L along the longitudinal direction of the dividing line 11.

[0044] As shown in (C) of Figure 6, by performing the second processing step, both ends 30 included in the range of the focal spot Sc are each irradiated with the laser beam L and removed, and a second processing groove 15 wider than the first processing groove 14 formed in the first processing step is formed between adjacent chips 12 in the Y-axis direction.

[0045] In the second processing step, as a result of removing the end portion 30 that functioned as a protective wall in the first processing step, burrs Qc generated when forming the second processing groove 15 adhere to the chip 12 located on both sides of the second processing groove 15, as shown in FIG. 6C. However, since the volume of the end portion 30 removed in the second processing step is smaller than the volume of the original TEG 13 that existed before the first processing step, the burrs Qc generated in the second processing step, in which a small amount of the metal pattern is removed, are much smaller than the burrs Qa that adhere to the chip 12 in the processing method of the comparative example shown in FIG. 4. Therefore, removing the burrs Qc after the second processing step is easy and does not require much effort, and chips 12 with excellent processing quality can be efficiently manufactured.

[0046] The smaller the volume of the end portion 30 removed in the second processing step, the more effective it is to reduce the size of the burrs Qc generated in the second processing step. It is preferable that at least the volume of the structure removed in the first processing step (the central portion of the TEG 13 in the width direction of the planned division line 11) is larger than the volume of the structure removed in the second processing step (the end portions 30 on both sides in the width direction of the planned division line 11). More detailed conditions regarding the proportion of the end portions of the structure to be left in the first processing step will be described later with reference to FIG. 12.

[0047] Although the spot diameter of the focused spot of the laser beam L is made different between the first processing step and the second processing step, the laser processing conditions other than the spot diameter may be set to the same conditions or different conditions between the first processing step and the second processing step. Examples of the laser processing conditions other than the spot diameter include the output of the laser beam L from the laser oscillator 25 and the processing interval in the longitudinal direction of the planned division line 11 (the distance between the centers of adjacent focused spots).

[0048] The control unit 24 may set the output of the laser beam L irradiated in the first processing step and the output of the laser beam L irradiated in the second processing step to the same output or different outputs. If the volume of the structure to be removed in the first processing step is larger than the volume of the structure to be removed in the second processing step, a higher ablation processing capability is required for the first processing step than for the second processing step. Conversely, the ablation processing capability required for the second processing step is relatively lower than that of the first processing step. Therefore, when the output of the laser beam L is set to be different for each processing step, the control unit 24 preferably sets the output of the laser beam L irradiated in the second processing step to be lower than the output of the laser beam L irradiated in the first processing step. This setting allows a lower-output laser beam L to be used in the second processing step, in which laser irradiation is performed at a position closer to the chips 12 in the width direction of the planned division lines 11, thereby reducing the effect of the laser beam L on the chips 12 (such as a decrease in flexural strength due to heat generation in the chips 12). This also results in energy savings in the second processing step.

[0049] The control unit 24 may set the distance Tb between the centers of the focal spots Sb of the laser beam L irradiated in the first processing step and the distance Tc between the centers of the focal spots Sc of the laser beam L irradiated in the second processing step to be the same distance or different distances. In the processing example shown in FIG. 7 , the control unit 24 sets the distance Tb between the centers of the focal spots Sb in the first processing step to be shorter than the distance Tc between the centers of the focal spots Sc in the second processing step. By setting them in this manner, in the first processing step, where the volume of the structure to be removed is large, the laser beam L can be irradiated at a high density with narrow irradiation intervals in the longitudinal direction of the division line 11, thereby performing ablation processing with high energy per unit area. Meanwhile, in the second processing step, where the volume of the structure to be removed is small, the laser beam L can be irradiated at a low density with wide irradiation intervals in the longitudinal direction of the division line 11, thereby performing ablation processing with excellent energy efficiency and time efficiency.

[0050] As described above, the control unit 24 appropriately sets the output of the laser beam L and the spacing of the focused spots according to the amount of structure removed in each of the first and second processing steps, thereby realizing laser processing optimized for each processing step and efficiently forming the first processing groove 14 and the second processing groove 15 while suppressing burrs adhering to the chip 12.

[0051] The processing method of the second embodiment will be described with reference to Fig. 8. The first processing step shown in Fig. 8(A) has the same processing content as the first processing step of the first embodiment, and irradiates a laser beam L having a spot diameter Rb of a focused spot Sb smaller than the length Ha of the TEG 13 in the width direction of the planned division line 11, leaving end portions 30 on both sides of the width direction of the planned division line 11, and forming a first processed groove 14 between the end portions 30 on both sides.

[0052] In the second processing step shown in FIG. 8B, the spot diameter Rb of the focused spot Sb is set to the same value as in the first processing step, and the laser beam L is irradiated onto the end portion 30 remaining in the first processing step. Because the spot diameter Rb of the focused spot Sb is large enough not to simultaneously cover both end portions 30, the laser processing is performed in two steps. First, the irradiation position is set so that the range of the focused spot Sb includes the end portion 30 on one side in the width direction of the division line 11, and the laser beam L is irradiated along the division line 11 for the first time to remove the end portion 30 on one side. Next, the irradiation position is set so that the range of the focused spot Sb includes the end portion 30 on the other side in the width direction of the division line 11, and the laser beam L is irradiated along the division line 11 for the second time to remove the end portion 30 on the other side. As a result, a second processed groove 15 is formed, as shown in FIG. 8C. The laser beam L may be branched in the Y-axis direction to form two focused spots Sb in the width direction of the division line 11.

[0053] As with the processing method of the first embodiment, in the processing method of the second embodiment, in the first processing step, the first processing groove 14 is formed while leaving the end portions 30 on both sides of the width direction of the planned division line 11, and in the second processing step, the end portions 30 on both sides are removed to form the second processing groove 15.This prevents burrs Qb from adhering to the chip 12 at the stage when the first processing groove 14 is formed, and also reduces the burrs Qc adhering to the chip 12 at the stage when the second processing groove 15 is formed.

[0054] Furthermore, in the processing method of the second embodiment, the first processing step and the second processing step are performed using the laser beam L having the same spot diameter Rb, so there is no need to take the time to change the spot diameter of the laser beam L, and it is easy to set the processing conditions in the laser irradiation unit 22. Moreover, unlike the laser irradiation unit 22, the method can also be applied to a type of laser irradiation unit in which the spot diameter of the laser beam is not variable.

[0055] The processing method of the third embodiment will be described with reference to Fig. 9. The first processing step shown in Fig. 9(A) has processing content similar to that of the first processing step of the first embodiment, and irradiates a laser beam L having a spot diameter Rb of a focused spot Sb smaller than the length Ha of the TEG 13 in the width direction of the planned division line 11, leaving end portions 30 on both sides of the width direction of the planned division line 11, and forming a first processed groove 14 between the end portions 30 on both sides.

[0056] In the second processing step shown in FIG. 9B, the spot diameter Rd of the focused spot Sd of the laser beam L is set smaller than the spot diameter Rb of the focused spot Sb in the first processing step, and the laser beam L is irradiated onto the end portion 30 remaining in the first processing step. Because the spot diameter Rd of the focused spot Sd is large enough not to simultaneously cover both end portions 30, the laser processing is performed in two stages. First, the irradiation position is set so that the range of the focused spot Sd includes the end portion 30 on one side in the width direction of the division line 11, and the laser beam L is irradiated along the division line 11 for the first time to remove the end portion 30 on one side. Next, the irradiation position is set so that the range of the focused spot Sd includes the end portion 30 on the other side in the width direction of the division line 11, and the laser beam L is irradiated along the division line 11 for the second time to remove the end portion 30 on the other side. As a result, a second processed groove 15 is formed, as shown in FIG. 9C. The laser beam L may be branched in the Y-axis direction to form two focused spots Sd in the width direction of the division line 11.

[0057] As with the processing method of the first embodiment, in the processing method of the third embodiment, in the first processing step, the first processing groove 14 is formed while leaving the end portions 30 on both sides of the width direction of the planned division line 11, and in the second processing step, the end portions 30 on both sides are removed to form the second processing groove 15.This prevents burrs Qb from adhering to the chip 12 at the stage when the first processing groove 14 is formed, and also reduces the burrs Qc adhering to the chip 12 at the stage when the second processing groove 15 is formed.

[0058] Furthermore, in the processing method of the third embodiment, in the second processing step, the laser beam L is not irradiated overlapping the area where the first processing groove 14 was formed in the previous first processing step, but the laser beam L having a narrowed spot diameter Rd is irradiated to the area of ​​the end portion 30 to be removed, so that the power of the laser beam L can be used efficiently to achieve energy-saving processing.

[0059] In the processing methods of the second and third embodiments, the laser processing conditions other than the spot diameter (such as the output of the laser beam L and the distance between the centers of adjacent focused spots) can be set in the same way as in the first embodiment. That is, the laser processing conditions other than the spot diameter (such as the output of the laser beam L and the distance between the centers of adjacent focused spots) can be set to the same value in the first processing step and the second processing step, or the laser processing conditions other than the spot diameter can be set differently.

[0060] In the processing methods of the second and third embodiments, when laser processing conditions other than the spot diameter are set differently, for example, the control unit 24 sets the output of the laser beam L irradiated in the second processing step to be smaller than the output of the laser beam L irradiated in the first processing step. Also, the control unit 24 sets the distance between the centers of adjacent focused spots Sb in the first processing step to be smaller than the distance between the centers of adjacent focused spots Sb, Sd in the second processing step. These settings make it possible to achieve processing that is optimized for each of the first processing step, in which the volume of the structure to be removed is large, and the second processing step, in which the volume of the structure to be removed is small.

[0061] 10, a plurality of TEGs 16 are arranged at positions offset from the center of the width direction of the dividing line 11. A non-metallic structure 17 consisting of a non-metallic pattern is arranged on the dividing line 11 at a position offset to the opposite side of the plurality of TEGs 16 in the width direction of the dividing line 11. The chip 12 arranged at a position closer to the TEG 16 in the width direction of the dividing line 11 is referred to as a first chip 121, and the chip 12 arranged at a position closer to the non-metallic structure 17 is referred to as a second chip 122.

[0062] 11 shows a processing method of the fourth embodiment, in which a wafer 10 having a TEG 16 and non-metallic structures 17 arranged on a dividing line 11 is processed. In a first processing step shown in FIG. 11(A), the control unit 24 sets the spot diameter Re of the focused spot Se of the laser beam L so as to cover a part of the TEG 16 and the entire non-metallic structures 17 in the width direction of the dividing line 11. That is, the spot diameter Re of the focused spot Se is a size that includes a part of the TEG 16, the entire non-metallic structures 17, and the space between the TEG 16 and the non-metallic structures 17 in the width direction of the dividing line 11. The spot diameter Re of the focused spot Se is larger than the length Hb of the TEG 16 in the width direction of the dividing line 11. Note that the non-metallic structures 17 do not necessarily have to be formed. When no non-metallic structure 17 is formed on the dividing line 11, the spot diameter of the focused spot of the laser beam L in the first processing step may be such that it covers at least a part of the length Hb of the TEG 16.

[0063] Next, the control unit 24 sets the irradiation position of the laser beam L in the width direction of the planned dividing line 11 so as to leave the end 31 of the TEG 16 closer to the first chip 121, and sequentially changes the irradiation position of the laser beam L (position of the focused spot Se) on the wafer 10 in the longitudinal direction of the planned dividing line 11, thereby performing ablation processing using the laser beam L along the longitudinal direction of the planned dividing line 11.

[0064] 11(B), by performing the first processing step, the portions of each of the multiple TEGs 16 on the division line 11 that are included in the range of the focused spot Se and that are irradiated with the laser beam L (the region on the second chip 122 side) are removed, and one end portion on the first chip 121 side that is outside the range of the focused spot Se remains as an end portion 31. Moreover, the non-metallic structure 17 on the division line 11 is entirely included in the range of the focused spot Se in the width direction of the division line 11, and therefore is completely removed in the first processing step. As a result, a first processing groove 18 is formed in the region excluding the end portion 31 that remains near the first chip 121.

[0065] The burrs Qd generated as a result of machining the TEG 16 when forming the first machining groove 18 are attached to the upper part of the remaining end 31. That is, in the first machining step, the end 31 left on one side of the width direction of the division line 11 functions as a protective wall that prevents burrs from adhering to the first chip 121 located closer to the TEG 16. As for the second chip 122 farther from the TEG 16, since the distance from the TEG 16 is large, even if the region of the TEG 16 facing the second chip 122 is removed in the first machining step (even if the end is not left), the burrs do not reach the second chip 122. In this way, when there is a deviation in the distance of the TEG 16 to the chips 12 on both sides, the effect of reducing burrs on the chip 12 can be achieved by leaving only the end 31 of the TEG 16, including the end closest to the chip 12, in the first machining step.

[0066] Even if the non-metallic structure 17 is entirely removed in the first processing step, no burrs are generated that would adhere to the second tip 122. Therefore, when the first processing step is performed, no burrs are attached to the second tip 122 on the side farther from the TEG 16.

[0067] In the second processing step shown in FIG. 11B, the spot diameter Rf of the focused spot Sf of the laser beam L is set smaller than the spot diameter Re of the focused spot Se in the first processing step, and the laser beam L is irradiated onto the end portion 31 left in the first processing step. Similar to the spot diameter Rd of the focused spot Sd in the third embodiment (see FIG. 9B), the spot diameter Rf of the focused spot Sf is set to the minimum size that covers the width of the end portion 31. Then, the irradiation position is set so that the range of the focused spot Sf includes the end portion 31 in the width direction of the planned division line 11, and the laser beam L is irradiated along the planned division line 11 to remove the end portion 31. As a result, a second processed groove 19 is formed as shown in FIG. 11C. Burrs Qe generated when removing the end portion 31 adhere to the first chip 121.

[0068] In the processing method of the fourth embodiment, in the first processing step, the first processing groove 18 is formed leaving the end portion 31 on one side of the width direction of the planned division line 11, and in the second processing step, the end portion 31 is removed to form the second processing groove 19.Therefore, when the first processing groove 18 is formed, burrs Qd are prevented from adhering to the chip 12 (first chip 121 and second chip 122), and when the second processing groove 19 is formed, burrs Qe adhering to the chip 12 (first chip 121) can be reduced in size.

[0069] In the processing method of the fourth embodiment, the laser processing conditions other than the spot diameter (such as the output of the laser beam L and the distance between the centers of adjacent focused spots) can be set in the same way as in the first embodiment. That is, the laser processing conditions other than the spot diameter (such as the output of the laser beam L and the distance between the centers of adjacent focused spots) can be set to the same value in the first processing step and the second processing step, or the laser processing conditions other than the spot diameter can be set differently.

[0070] In the processing method of the fourth embodiment, when the laser processing conditions other than the spot diameter are set differently, for example, the control unit 24 sets the output of the laser beam L irradiated in the second processing step to be smaller than the output of the laser beam L irradiated in the first processing step. Furthermore, the control unit 24 sets the distance between the centers of adjacent focused spots Se in the first processing step to be smaller than the distance between the centers of adjacent focused spots Sf in the second processing step. These settings make it possible to achieve processing that is optimized for each of the first processing step, in which the volume of the structure to be removed is large, and the second processing step, in which the volume of the structure to be removed is small.

[0071] In the processing methods of the above embodiments, it is preferable that at least the volume of the metal structure removed in the first processing step (the removed portion of TEG 13 or TEG 16) is larger than the volume of the metal structure removed in the second processing step (end 30 or end 31). As described above, the smaller the volume of the structure removed in the second processing step, the greater the effect of reducing the size of burrs generated in the second processing step.

[0072] The table shown in Figure 12 is the experimental results showing the relationship between the processing conditions for the end of the metal structure to be left in the first processing step and the final processing result (the burr occurrence status of the chip after the second processing step).

[0073] The numbers on the left side of the table in Figure 12 are the ratios of the widths (lengths in the width direction of the planned division line 11) of the ends (ends 30, 31) of the metal structures that remain in the first processing step to the widths (lengths in the width direction of the planned division line 11) of the original metal structures (TEG13, TEG16) that were placed on the planned division line 11 before the first processing step was performed. The smaller the number, the smaller the ratio of the widths of the ends of the metal structures that remain in the first processing step, and the smaller the ratio of the volume of the portion that remains in the first processing step. In other words, the larger the number, the larger the ratio of the volume of the remaining portion that needs to be removed in the second processing step.

[0074] The right side of the table in Figure 12 shows the results of determining whether the height of the burr attached to the chip 12 after the second processing step is below a reference value (tolerance), with "◯" indicating a good result below the reference value and "×" indicating a result above the reference value. When a TEG 13 having a large width relative to the planned division line 11 is placed, as in Figure 2, and burrs occur on the chips 12 on both sides of the planned division line 11, the height of the burr on each of the chips 12 on both sides is determined. When a TEG 16 is placed offset from the center of the planned division line 11 in the width direction, as in Figure 10, and burrs occur only on the chip 12 (first chip 121) on one side of the planned division line 11, the height of the burr may be determined only on the chip 12 on which the burr occurs.

[0075] As can be seen from the experimental results, when the width ratio of the ends (ends 30 and 31) of the metal structure left in the first processing step is 45% or more of the width of the original structure, the amount of the remaining part removed in the second processing step increases, causing the burr height to exceed the standard value, and even if the first and second processing grooves are formed in stages, a sufficient effect cannot be obtained in reducing the adhesion of burrs to the tip 12. In other words, there was not much difference in the burr generation situation compared to when the metal structure was removed in one processing step without leaving the ends, as in the comparative examples of Figures 4 and 5.

[0076] Furthermore, if the proportion of the width of the end of the metal structure to be left in the first processing step is set to 1% or less of the width of the original structure, the end will not remain and the entire metal structure will be removed in the first processing step, resulting in variations in the processing conditions and making it difficult to reliably leave an end of the desired width.

[0077] From the above experimental results, in terms of the dimensional relationship in the width direction of the planned division line 11, it is preferable that the ratio of the width of the end portion of the metal structure to be left in the first processing step to the width of the metal structure before processing is in the range of approximately 2% to 40%.

[0078] As described above, according to the wafer processing method of each of the above embodiments, in the first processing step, the ends 30, 31 of the TEGs 13, 16, which are structures on the planned dividing line 11, are left to form the first processing grooves 14, 18, and in the second processing step, the ends 30, 31 are removed to form the second processing grooves 15, 19, thereby reducing burrs that adhere to the chip when forming the processing grooves along the planned dividing line 11.

[0079] Furthermore, by dividing the wafer 10 in which grooves have been formed by the above processing method along the grooves, a plurality of chips 12 can be manufactured.

[0080] Specifically, if the first grooves 14 and 18 formed in the first processing step and the second grooves 15 and 19 formed in the second processing step are full-cut grooves that penetrate the wafer 10 in the thickness direction, the wafer 10 is divided into individual chips 12 at the stage where these full-cut grooves are formed. When processing is performed with the processing device 20, by attaching tape (not shown) to the back side of the wafer 10 opposite the front side on which the chips 12 are formed, the multiple chips 12 are held in a predetermined positional relationship via the tape, even in a state where the wafer 10 has been divided into individual chips 12 by the full-cut grooves. Therefore, each chip 12 can be deburred while held via the tape.

[0081] When the first processed grooves 14, 18 formed in the first processing step and the second processed grooves 15, 19 formed in the second processing step are bottomed half-cut grooves that do not penetrate the wafer 10 in the thickness direction, the wafer 10 is divided using the half-cut grooves as the division starting points by applying an external force to the wafer 10 in a state where the half-cut grooves are formed, or by forming a modified layer inside the wafer 10 along the intended division lines 11 in addition to the half-cut grooves and then applying an external force. Deburring of the chips 12 may be performed before the half-cut grooves are formed and the wafer 10 is divided, or may be performed after the wafer 10 has been divided into individual chips 12, as in the case of the full-cut grooves described above.

[0082] In the wafer processing methods of the above embodiments, the first grooves 14 and 18 are formed in the first processing step, and the second grooves 15 and 19 are formed in the second processing step by irradiation with a laser beam, but the method of forming the grooves in each processing step is not limited to this. For example, the first grooves in the first processing step can be formed by cutting with a cutting blade, and the second grooves in the second processing step can be formed by irradiation with a laser beam.

[0083] In the wafer processing methods of the above embodiments, one first processing groove 14, 18 is formed for one planned division line 11 in one processing operation, but as a modification of the first processing step, the formation of the first processing groove may be performed in multiple stages. For example, when forming the first processing groove, a groove with a small width may be formed first, and the width of the groove may be gradually increased until the first processing groove is completed.

[0084] In the wafer processing methods of the first to third embodiments described above, in the first processing step, only the end portions 30 on both sides of the TEG 13 are left, but as a variation of the first processing step, multiple first processing grooves may be formed between the end portions 30 on both sides, and a portion of the central part of the TEG 13 may be left between the multiple first processing grooves.

[0085] A processing method according to a fifth embodiment shown in FIG. 13 illustrates such a modification. In a first processing step shown in FIG. 13A, the control unit 24 sets the spot diameter Rg of the focused spot Sg of the laser beam L irradiated onto the TEG 13 to less than half the length Ha of the TEG 13 in the width direction of the dividing line 11. The laser beam L is then irradiated onto two locations spaced apart in the width direction of the dividing line 11. As a result, as shown in FIG. 13B, two first grooves 32 are formed at the two locations irradiated with the laser beam L, with end portions 30 remaining outside the two first grooves 32 and central portions 33 remaining inside the two first grooves 32. The laser beam L may be branched in the Y-axis direction to form two focused spots Sg in the width direction of the dividing line 11. The number of first grooves 32 may be three or more.

[0086] 13(B), the control unit 24 sets the spot diameter Rc of the focused spot Sc of the laser beam L to be equal to or greater than the length Ha of the original TEG 13 in the width direction of the dividing line 11. This setting is similar to the second processing step of the first embodiment (see FIG. 6(B)). Then, the control unit 24 sets the position of the laser irradiation part 22 so that the range of the focused spot Sc in the width direction of the dividing line 11 includes both end parts 30 and the central part 33, and causes the laser beam L to be irradiated toward the wafer 10.

[0087] As shown in (C) of Figure 13, by performing the second processing step, both side ends 30 and the central portion 33 included in the range of the focal spot Sc are each removed by irradiation with the laser beam L, and a second processing groove 34 wider than the two first processing grooves 32 formed in the first processing step is formed between adjacent chips 12 in the Y-axis direction.

[0088] In the second processing step, the central portion 33 is removed together with the end portions 30 on both sides, but since the central portion 33 is far away from the chips 12 located on both sides of the planned dividing line 11, large burrs are unlikely to occur on the chips 12 due to the removal of the central portion 33. Furthermore, since the combined volume of the end portions 30 and the central portion 33 removed in the second processing step is smaller than the volume of the original TEG 13 that existed before the first processing step, it is possible to reduce the burrs Qc that occur on the chips 12 in the second processing step, in which a small amount of the metal pattern is removed.

[0089] In other words, the first processing groove formed in the first processing step only needs to be configured so that at least one end of the original structure remains as an end, and there is freedom of choice regarding the processing procedure for forming the first processing groove and the number of first processing grooves in one planned division line.

[0090] The embodiments of the present invention are not limited to the above-described embodiments and modifications, and may be variously changed, substituted, or modified without departing from the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial Applicability]

[0091] As described above, according to the present invention, it is possible to reduce burrs that adhere to chips when forming grooves along the planned dividing lines, thereby contributing to improving the productivity of manufacturing chips from wafers. [Explanation of symbols]

[0092] 10: Wafer 11: Planned division line 12: Tip 13:TEG (Structure) 14:First machining groove 15:Second processing groove 16:TEG (Structure) 17: Non-metallic structures 18: First machining groove 19:Second processing groove 20: Processing equipment 21: Holding table 22: Laser irradiation unit 23: Imaging unit 24: Control unit 25: Laser oscillator 26: Condensing optical system 27:Optical system adjustment section 28: Horizontal movement mechanism 29: Lifting mechanism 30: Edge 31: Edge 32:First machining groove 33: Central part 34:Second processing groove 121: First chip 122: Second chip L: Laser beam Qa~Qe: Bali Ra~Rg: Spot diameter Sa~Sg: Focusing spots

Claims

1. A wafer processing method for forming a processing groove in a wafer along a planned dividing line, comprising: a structure is formed on at least a portion of the planned dividing line; a first processing step of forming a first processing groove that leaves an end portion including at least one end in a width direction of the planned dividing line of the structure; a second processing step of forming a second processing groove along the planned dividing line to remove the end portion remaining in the first processing step; A wafer processing method comprising:

2. 2. The wafer processing method according to claim 1, wherein the first groove and the second groove are formed by irradiating the wafer with a laser beam.

3. 2. The wafer processing method according to claim 1, wherein the volume of the structure removed in the first processing step is larger than the volume of the structure removed in the second processing step.

4. 2. The wafer processing method according to claim 1, wherein the output of the laser beam irradiated in the second processing step is smaller than the output of the laser beam irradiated in the first processing step.

5. 2. A wafer processing method according to claim 1, wherein the distance between the centers of adjacent focused spots of the laser beam at the position irradiated on the wafer is smaller in the first processing step than in the second processing step.

6. A wafer processing method according to any one of claims 1 to 5, characterized in that the structure to be left in the first processing step is 2% or more and 40% or less of the width direction length of the planned dividing line of the structure.

7. A chip manufacturing method for manufacturing a plurality of chips by dividing a wafer by at least one of the first groove and the second groove according to claim 1.

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